Method for manufacturing a structural component for a motor vehicle

ABSTRACT

A method for manufacturing a component of a vehicle structure or vehicle seat structure is provided that includes, but is not limited to pressing a starting material through a die in order to produce an extruded product, separating a section from the extruded product, and forming the separated section into the component. A varying wall thickness of the separated section is produced during the pressing through the die.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Patent Application No. 102009017374.9, filed Apr. 14, 2009, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention pertains to a method for manufacturing a component of a vehicle seat structure for a motor vehicle seat or a motor vehicle structure, as well as to a motor vehicle seat or a motor vehicle with a structure that features several components, at least one of which was manufactured by means of such a method.

BACKGROUND

The backrest frames of motor vehicle seats frequently consist of metal and have the shape of an upside down U. The limbs of the U are referred to as the longitudinal beams that are connected by a crossbeam. The backrest frame needs to withstand the highest loads when the vehicle is subjected to longitudinal impacts and the torso and head of the person using the seat are thrown against the backrest and the headrest. In this case, high loads occur, in particular, at the connecting points between the backrest frame and the seat frame, as well as at the connecting points between the backrest frame and the headrest.

In order to save material and weight, the components of the supporting structure of a vehicle seat should only have a cross-sectional surface that is adapted to the respective maximum load at all locations. In frequently used backrest frames that are formed of a bent round tube, a minimum cross-sectional surface required at locations subjected to maximum loads also needs to be used at locations, at which only low loads occur.

In frames that are realized in the form of die cast magnesium parts, the cross-sectional surface can be adequately adapted to the expected load. However, certain restrictions result from the minimum wall thickness of the structural component caused by the casting technology. Other disadvantages are the high costs of the casting mould, the high material price, the low ductility of casting alloys and the high expenditures required for avoiding or detecting casting defects such as shrink holes or pores.

In frames that are formed of folded and bent sheets, limitations result from the fact that the sheets have the same thickness at all locations. A great sheet thickness is only required, for example, at the connecting points of the backrest frame to the seat frame and the headrest brackets or in the zones subjected to bending stress in the cross-sectional regions situated far from the neutral axis. A smaller wall thickness would be advantageous at all other locations because these locations are not subjected to any significant loads.

Consequently, EP 0 745 508 B1 proposes a method for manufacturing an approximately U-shaped frame of a backrest of a motor vehicle seat that consists of two longitudinal beams and a crossbeam, wherein a profiled part with a strong center zone that is followed on both sides by a weaker region and then an adjacent strong region is initially produced from an originally straight band-like, flat extruded product or rolled product with constant cross-sectional surface by means of subsequent rolling and trimming, and wherein this profiled part is subsequently bent into the U-shaped frame.

In this case, it is disadvantageous that the rolling process represents an additional production step required for realizing the different regions of the originally straight band-like, flat extruded product or rolled product with constant cross-sectional surface.

According to DE 43 33 500 A1 that does not concern the manufacture of a component of a vehicle structure or vehicle seat structure, it is necessary to subject an extruded profile to subsequent production steps, particularly to cut open and roll said profile. Alternatively, WO 00/29138 proposes to weld together adjacently arranged strips of different wall thickness in order to produce a profiled part with different wall thicknesses.

In view of the foregoing, at least one objective is to improve a structure for a motor vehicle seat or a motor vehicle and a method for manufacturing a component of such a structure. In addition, other objectives, desirable features, and characteristics will become apparent from the subsequent detailed description, and the appended claims, taken in conjunction with the accompanying drawings and this background.

SUMMARY

According to an embodiment of the invention, one or more components of a structure for a motor vehicle seat or a motor vehicle are manufactured by pressing a starting material through one or more dies in order to produce an extruded product. The extruded product may be manufactured, in particular, by means of impact extrusion or extrusion.

Subsequently, a section is separated from the extruded product, for example, by means of sawing, particularly with a band saw, cutting, particularly with a laser, or another separating method, wherein the separated section subsequently serves as a semi-finished product that is formed into the component. This may be realized, for example, by means of compressive deformation, particularly open-die forging, closed-die forging such as, in particular, forging, indentation forming and/or additional extrusion. Additionally or alternatively, the separated section may also be formed into the component by means of indirect compression, particularly cold drawing, deep drawing, spinning, plunging, upset bulging and/or hydroforming. The separated section may be additionally or alternatively formed into the component by means of tensile forming, particularly extending and/or expanding, and/or by means of bending, particularly wiping die bending and/or die bending.

According to an embodiment of the invention, a varying wall thickness of the separated section is already realized when the starting material is pressed through one or more dies such that said section already has a varying wall thickness transverse to the extruding direction prior to the additional forming.

This advantageously makes it possible to eliminate one or more additional rolling or welding steps after the extrusion in the manufacture of a structural component such that the manufacturing costs and the manufacturing time are reduced.

On the other hand, regions that are subjected to higher loads can be realized with greater wall thicknesses and therefore safer and regions that are subjected to lower loads can be realized with smaller wall thicknesses and therefore lighter and with less material, namely without requiring an additional production step between the extrusion and the forming into the component of the structure.

This method makes it possible, in particular, to manufacture a crossbeam of a frame-like backrest structure, in which the separated section advantageously has a greater wall thickness at least in the region of a headrest receptacle. This method likewise makes it possible to manufacture, for example, a seat shell, wherein the separated section advantageously has a greater wall thickness at least in the region of a bearing point, particularly an adjustable pivot joint for producing a connection with a backrest. Alternatively, this inventive method also makes it possible to manufacture other components of a motor vehicle structure such as, for example, car body or paneling components.

With respect to the formability during the extrusion process, the strength and the weight, magnesium or a magnesium alloy is particularly advantageous as a starting material. In this case, it may be particularly advantageous to form the separated section into the component by means of hot forming, preferably by utilizing a heating process realized prior to or during the extrusion through the die. In comparison with conventional methods used so far, in which magnesium sheets with homogenous wall thickness were initially extruded or continuously cast and these sheets were subsequently cold-formed, the hot forming of the separated section that is still hot from the extrusion or continuous casting process provides superior formability, a superior texture and/or energy savings.

According to one preferred embodiment, the extruded product has a smaller width than the finished component during the extrusion through the die. This makes it possible, for example, to initially produce a narrow sheet that is subsequently widened, particularly in regions with greater wall thickness, by means of forming processes, preferably hot forming, particularly by utilizing a heating process realized prior to or during the extrusion through the die, such that wider structural components can be manufactured with narrower dies. Other advantageous additional developments of the present invention result from the dependent claims and the following description of preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and

FIG. 1A shows a step of a manufacturing method according to the state of the art;

FIG. 1B shows a separated section according to the state of the art manufactured in the step shown in FIG. 1A;

FIG. 1C shows a crossbeam according to the state of the art formed from the separated section shown in FIG. 1B;

FIG. 2A shows a step of a manufacturing method according to one embodiment of the present invention in the form of a representation that corresponds to FIG. 1A;

FIG. 2B shows a separated section manufactured in the step shown in FIG. 2A in the form of a representation that corresponds to FIG. 1B;

FIG. 2C shows a crossbeam formed of the separated section shown in FIG. 2B in the form of a representation that corresponds to FIG. 1C;

FIG. 3A shows a frame-like backrest structure with the crossbeam according to FIG. 2C;

FIG. 3B shows the crossbeam according to FIG. 3A; and

FIG. 4 shows a seat shell according to another embodiment of the present invention.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description.

FIG. 1A shows a step of a manufacturing method according to the state of the art, in which a magnesium alloy is pressed through a die 2′ in the y-direction of the coordinate system illustrated in FIG. 1A in order to produce a sheet-like extruded product 1′ with constant wall thickness in the x-direction, i.e., the transverse direction, wherein the height is measured in the z-direction. FIG. 1B shows a cross section through the extruded product 1′ in the x-z plane, i.e., perpendicular to the extruding or pressing direction y, wherein the constant wall thickness is illustrated in this cross section.

Subsequently, a section is separated from the extruded product 1′ by means of a cutting process and formed into the crossbeam 3′ for a backrest of a vehicle seat structure shown in FIG. 1C in another not-shown forming process. In FIG. 1, “y” indicates the extruding or pressing direction of the original extruded product 1′. Due to the constant wall thickness of the separated section, the crossbeam formed thereof also has an identical wall thickness at all locations and therefore is undersized in regions that are subjected to higher loads or oversized in regions that are subjected to lower loads.

FIG. 2A to FIG. 2C respectively show a crossbeam of a frame-like backrest structure for a motor vehicle seat and its manufacture according to one embodiment of the present invention, namely in the form of representations that correspond to FIG. 1A to FIG. 1C. According to an embodiment of the invention, an extruded product 1 with a wall thickness that varies in the x-direction, i.e., in the transverse direction, is already formed when the magnesium alloy is pressed through the die 2. In the cross section according to FIG. 2B, an edge region 1.1 with greater wall thickness and an adjacent region 1.2 with smaller wall thickness are shown.

If the crossbeam 3 is now produced from this extruded product in the above-described fashion by separating a certain section and subsequent forming, the region 1.1 with the greater wall thickness forms a headrest receptacle 3.1 of the crossbeam 3 as indicated with broken lines in FIG. 2C if this region 1.1 that extends in the profile direction y is bent during the forming process. This makes it possible to manufacture an advantageous crossbeam 3, the headrest receptacle 3.1 of which is subjected to higher loads and therefore has a greater wall thickness while material and weight are saved due to smaller wall thicknesses in frontal and lateral regions that are subjected to lower loads, namely without having to separately produce an extruded profile with varying wall thickness between the extrusion according to FIG. 2A and the forming into the final shape of the crossbeam 3 according to FIG. 2C by means of rolling or welding together strips.

FIG. 3A shows the frame-like backrest structure 4 with two lateral parts and the aforementioned upper crossbeam 3 that is illustrated in an enlarged fashion in FIG. 3B such that, in particular, headrest guide receptacles 3.2 in the region of the headrest receptacle 3.1 are clearly visible.

FIG. 4 shows a seat shell 5 that was manufactured accordingly by means of extruding and subsequent forming into the final shape, namely without an intermediate rolling process for changing the wall thickness of the extruded product 1. Since one edge region 1.1 was once again realized with a greater wall thickness and rear bearing points 5.1 of the seat shell 5 are produced with this edge region during the forming process, the bearing points 5.1 that are subjected to higher loads also have a greater wall thickness while material and weight are saved in a front region that is subjected to lower loads.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. 

1. A method for manufacturing a component of a motor vehicle structure, comprising the steps of: pressing a starting material through a die in order to produce an extruded product; separating a section from the extruded product to produce a separated section comprising a varying wall thickness transverse to an extruding direction (y) prior to forming an produced during the pressing the starting material through the die; and forming the separated section into the component.
 2. The method of claim 1, wherein the component is a vehicle seat structure for a motor vehicle seat.
 3. The method according to claim 1, wherein at least one region of the separated section that is subjected to a higher load comprises has a greater wall thickness than at least one other region that is subjected to a lower load.
 4. The method according to claim 3, wherein the component is a crossbeam of a frame-like backrest structure and the separated section comprises the greater wall thickness in a region of a headrest receptacle.
 5. The method according to claim 3, wherein the component is a seat shell and the separated section comprises the greater wall thickness in a region of a bearing point.
 6. The method according to claim 1, wherein the starting material comprises magnesium.
 7. The method according to claim 1, wherein the starting material comprises aluminum.
 8. The method according to claim 1, wherein the starting material comprises a magnesium alloy.
 9. The method according to claim 1, wherein the starting material comprises an aluminum alloy.
 10. The method according to claim 1, wherein the extruded product is produced by impact extrusion.
 11. The method according to claim 1, wherein the separated section is formed into the component with a compressive deformation.
 12. The method according to claim 11, wherein the compressive deformation is an open-die forging.
 13. The method according to claim 11, wherein the compressive deformation is a closed-die forging.
 14. The method according to claim 11, wherein the separated section is formed into the component by hot forming.
 15. The method according to claim 14, wherein the hot forming utilizes a heating process.
 16. The method according to claim 1, wherein the extruded product has a smaller width than a finished component.
 17. The method according to claim 1, wherein the extruded product is realized in a sheet-like fashion. 